Phasing circuit for network protectors



Nov. 27, 1934. A, w 1,982,337

PHASING CIRCUIT FOR NETWORK PROTECTORS Filed Dec; 21, 1952 2 Sheets-Sheet 1 Fig.1.

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WITNESSES: INVENTOR f M ran 14. Boslwick 5 y 'W ATTNEY Nov. 27, 1934. BOSTWICK 1,982,337

PHASING CIRCUIT FOR NETWORK PROTECTORS Filed Dec. 21, 1952 2 Sheets-Sheet 2 1'77. 5. Fry. 4. Fly. 5.

E EA Ec E5 E]; v EA WITNESSES: INVENTOR M Myron r4. Bostwz'ck 2 I v BY M ATT EY Patented Nov. 27, 1934 UNITED STATES PATENT OFFICE PHASING CIRCUIT FOR NETWORK PROTECTORS tion of Pennsylvania Application December 21, 1932, Serial No. 648,208

6 Claims.

My invention relates to automatic network protectors for polyphase alternating-current circuits, and particularly to phase circuits for use in such protectors.

My invention is particularly applicable to polyphase network protectors of the phase-sequence type, in which a single-element induction disc relay controls the opening of the protector circuit breaker in accordance with the reverse positive phase-sequence power flow through the protector and controls the closing of the protector circuit breaker in accordance with the magnitude and phase relationship of the polyphase voltages on either side of the protector. An example of such a phase-sequence protector is disclosed in the copending application of R. E. Powers and H. R. Searing, Serial No. 648,207, filed Dec. 21, 1932 and assigned to the Westinghouse Electric 8: Manufacturing Company.

As the induction disc relay used in such protectors is of the single-element type, although the network and feeder voltages to be compared during the closing operation are polyphase, some provision must be made for preventing the closure of the protector circuit breaker in the event that one phase of feeder voltage is correct as compared with the corresponding phase of network voltage, but the remaining two phases of feeder voltage are reversed. In the above-mentioned application of Searing and Powers, a positive phase-sequence voltage network, connected to the feeder side of the protector is used for supplying one of the voltages to be compared during the phasing or closing operation of the protector. Upon the reversal of any two phases of feeder voltage, the output voltage of the positive phasesequence network becomes substantially zero, and the relay remains open. A transformer or a second positive phase-sequence voltage network is used on the network side of the protector to obtain a network component of phasing voltage.

It is an object of my invention to provide an improved and simplified phasing circuit for use in protectors of the type indicated above.

Another object of my invention is to provide a phasing circuit for protectors of the type indicated above which shall not require auxiliary phase-sequence networks for use in the relay phasing circuits.

A further object of my invention is to provide a novel means for controlling the single-element relay in accordance with two independent phasing voltages.

Other objects of my invention will become evident from the following detailed description taken in conjunction with the accompanying drawings, in which Figure 1 is a diagrammatic view of the phasing circuits of an automatic protector embodying my invention.

Fig. 2 is a vector diagram showing the relationship of voltage and magnetic flux variables in the apparatus shown in Fig. 1.

Figs. 3 to 13 are vector diagrams showing the relationship of voltage variables in the apparatus shown in Fig. 1 under abnormal conditions, and

Figs. 14 and 15 are diagrammatic views of modified phasing circuits for use in the apparatus shown in Fig. 1.

Referring to Fig. 1 in detail, a distribution network 1 is connected to be supplied from a feeder 2 by means of a bank of transformers 3, the individual transformers of which are designated' by the reference characters 3a, 3b and 30, respectively. A protector circuit breaker 4 is interposed between the secondary windings of the transformer bank 3 and the network 1 for controlling the connection and disconnection of the feeder 2 and network 1. The bank of transformers 3 is preferably connected in delta on the feeder side and in star with neutral grounded on the network side, but may be connected in other ways known in the art.

The protector circuit breaker 4 is provided with a closing coil 4a controlled by a single-element induction-disc relay 5 and with suitable latching and tripping mechanism of well known type, indicated diagrammatically at 4t. As the present invention relates only to the closing operation of the protector circuit breaker, the connections for controlling the opening of the circuit breaker have for simplicity been omitted. It will be understood, however, that in a practical application of the invention, the tripping mechanism 4t would be connected in a well known manner with the relay 5, and the relay 5 would be provided with various elements, disclosed in detail in the above-mentioned.v application of Powers and Searing, for causing the circuit breaker 4 to open in response to reversed positive phase-sequence power.

The relay 5 consists of an induction disc assembly 5a mounted to rotate under the influence of a driving magnet 6 and a drag magnet '7 in a manner well understood in the art. The driving magnet 6 is provided with a potential winding 8, a phasing winding 9b and a second phasing winding 90 mounted upon pole members positionally displaced along the periphery of the induction disc. The induction disc assembly 5a is mechanically connected in any suitable manner to contact members 5b for completing circuits for the trip mechanism at of the circuit breaker 4 in one angular position of the induction disc assembly 5a, and for the closing coil 4a in a second angular position of the induction disc assembly So. I A spiral spring 50 is provided for biasing the induction disc assembly 5a into the closing position as shown in Fig. 1, to insure closure of the circuit breakers 4 when the distribution network 1 is deenergized.

An over-voltage adjusting loop, shown diagrammatically at Set, is provided for producing a biasing torque in opposition to and greater than the biasing torque of the spring 50 when the distribution network 1 is energized. The overvoltage adjusting loop 512 is preferably of the usual type comprising a fiat shading loop interposed between the pole member upon which the potential winding 8 is mounted and the induction disc.

The potential winding 8 isconnectecl to a phase-sequence voltage filter '10 to be energized in accordance with a positive symmetrical component of the polyphase voltage of the distributlon network 1. The phase-sequence filter 10 consists of an auto-transformer 10a, a reactor 10?) and a resistor 100. Th auto-transformer 10a is tapped at an intermedia e point to provide an output volage of a predetermined percentage, for example 40%, of the total voltage impressed on the auto-transformer. The constants of re actor 10b and resistor 16c are so related that the voltage drop across the resistor 10c is equal to the percentage mentionedabove, (40%) of the total voltage impressed on the reactor 10b and resistor 10c in series, but lags the latter voltage by a phase angle of 69. The terminals of the phase-sequence filter 10 are connected to the phases of the distribution network 1 in the order indicated by the subscripts a, b and c of the network conductors la, lb and 10. As exp ained in the above-mentioned application of Powers and Searing. a phase-secuence filter desi ned and connectsin the manner described above produces an output voltage proportional to the positive symmet "cal components of network voltage and laggin, the o-phase positive component by a phase an le of 60. The voltage impressed on the po ential w nding 8, when the distribution network 1 is ener zed. is accordingly proportional to the positive symmetrical components of network voltage and is disp aced 60 in phase po i ion. from the c-nhase positive component or 180 from the c--phase component.

The phasing w nd ng 92 connected in a phasing circuit 11, which includes an adiustable reactor 12 and a phasing lamp 13. The circuit 11 is connected across the c-phase main contact members of the circuit breaker 4. The phasing winding 92) is connected in a phasing circuit 14, which includes a saturable reactor 15 and a condenser 16. The phasing circuit 14 is connected across the b-phase main contact members of the circuit breaker 4. V

Thephasing lamp 1 5 is preferably of the tungsten filament type and has a high positive temperature coeiiicient of resistance. The constants of the reactor 12 and phasing lamp 13 are so related that under conditions of minimum resistance of the phasing lamp 153, the current in the phasing circuit 11 lags the voltage impressed thereon by a comparatively large phase angle, which for purposes of illustration will be assumed as 73. In practice this angle may be made larger or smaller by adjustment of the reactor 12, depending upon the protector closing characteristics desired.

Because of the positive temperature coefiicient of resistance of the phasing lamp 13, the resistance of the circuit 11 increases with increase oi current, so that at high values of current in the circuit 11, the phase angle of the latter circuit is greatly reduced.

The constants of the saturable reactor 15, condenser l6 and phasing winding 91) are so related that when the reactance of the saturable reactor 15 is a maximum, the inductive reactance of the phasing circuit 14 slightly predonrnates over the condensive reactance introduced by the condenser 16. The resistance of the entire circuit 14 is sufficiently large to reduce the phase angle of the circuit to a comparatively small value, for example 13. With large values of current in the circuit 14, however, the reactor 15 saturates, thereby reducing the inductive reactance of the circuit 14 and causing the condensive reactance to predominate and the current to lead the voltage by a variable phase angle dependent upon the degree of saturation or" the reactor 15.

The circuit breaker l is'provided with back auxiliary contact members 41), 4c and ed for opening the circuit of the closing coil 4a and the phasing circuits 11 and 14 respectively, when the circuit breaker 4 is closed.

Referring to Fig. 2, which shows the vector relationship of alternating voltages and fluxes in the apparatus shown in Fig. 1 under conditions of balanced network voltage, the net vork star voltages are indicated by the vectors Em, Elm, and Eon. For convenience, the c-phase vector Eon is shown in the vertical position.

As the voltage of the distribution network 1 is assumed to be balanced, the positive symmetrical components of network voltage are equal and coincident to the network star voltages, and the negative symmetrical components of network voltage are zero.

The voltage applied to the potential winding 8 is designated by the reference character Ep. As mentioned above, this voltage lags the a-phase positive component, which under balanced voltage conditions is identical with the voltages Ean, by a phase angle of 60. The voltage Ep impressed on the inductive potential winding 8, produces a potential flux component which lags the voltage Ep by a phase angle approaching 90, which for simplicity will be assumed as 90. The voltages impressed on the phasing circuits 11 and la produce flux components which cooperate in a well known manner with the flux component 5;) to produce a relay torque.

The maximum torque position of the flux component produced by the phasing circuit 14 is indicated by the vector 1l, in quadrature to the flux component (131:. As the phase angle of the phasing circuit 14 for small values of phasing voltage is assumed as 13 lagging. a small phasing voltage such as E14 must lead the flux component 14 by a phase angle of 13 to produce maximum torque in the relay 5. For larger values of phasing voltage, the phase angle of the phasing circuit 14 changes from lag to lead, requiring the phasing voltage to lag the phase position or" the i vector E14 to produce maximum relay torque.

The zero torque curve for the phasing circuit 14 is shown at T14. If the vector corresponding to the secondary voltage of the transformer 31) intersects the curve T14 in Fig. 2, the relay 5 produces a closing torque component, whereas if the vector corresponding to the secondary voltage of the transformer 31; fails to intersect the curve T14, the relay 5 produces a tripping torque component.

The maximum torque position of the flux component produced by the phasing circuit 11 is indic'ated by the vector 1 111, in quadrature to the flux component =p and opposite to the flux component (p14. As the phase angle of the circuit 11 is assumed as 73 for low values of phasing voltage, a given small phasing voltage E11 applied to the circuit 11 must lead the vector #111 by a phase angle of 73 to produce maximum torque in the relay 5. The upper portion of the zero torque curve T11 for the phasing circuit 11 is accordingly displaced approximately 17 from the vertical. It will be noted that the curve T11 bends at 17 to a greater angle from the vertical. This bend is caused by the reduction of power factor angle of the circuit 11 with increasing voltages applied to the circuit, because of the temperature coefficient of resistance of the phasing lamp 13, as explained above.

The operation of the apparatus shown in Fig. 1 may be set forth as follows: It is assumed that initially the network 1 and feeder 2 are deepergized and the circuit breaker 4 and relay 5 are in the positions shown in the figure. If the network 1 is now energized by voltage of normal phase-sequence and normal value, which for simplicity will be assumed to be balanced, the phasesequence' filter 10 energizes the potential winding 8 in accordance with a positive symmetrical component of network voltage. Because of the energization of the potential winding 8, the overvoltage adjusting loop 5dproduces a tripping torque in the relay 5 greater than the closing torque produced by the spring 50.

At the same time, voltage is applied to the phasing circuits 11 and 14. As the feeder 2 is at this time deenergized, the secondary voltages of the transformers 3b and 3c are zero. Referring to Fig. 2, the zero secondary voltages of the transformers 3b and 3c terminate at the origin and hence cannot intersect the curves T14 or T11 respectively. Both phasing circuits 11 and 14 accordingly act to produce strong tripping torques, which cooperate with the tripping torque produced by the over-voltage adjusting loop 5d to rotate the induction-disc assembly 5a into the tripping position.

If the feeder 2 is now energized by three phase voltage of correct phase-sequence as compared with the phase-sequence of voltage of the network 1 and of approximately normal magnitude, the secondary voltage of the transformer 31) terminates in the region near the end of the vector Ebn (Fig. 2), and the secondary voltage of the transformer 3c terminates near the end of the vector Eon. If the vectors corresponding to the secondary voltages of the transformers 3b and 3c are of sufficient magnitude and proper phase re lationship to intersect the curves T14 and T11, respectively, the phasing circuits 11 and 14 operate to produce closing torque components.

When the aggregate of closing torque produced by the phasing circuits 11 and 14 and the spring 5c, exceeds the tripping torque produced by the over-voltage adjusting loop 511, the relay 5 closes to cause the closure of the circuit breaker 4.

In the phasing operation described above, it will be noted that both the b-phase and c-phase voltages are compared by the single element relay 5 and closure occurs in response to the aggregate of two phasing torques. It will also be noted that rotated zero torque curves, similar to those of the usual separate phasing relay, are produced for bothphasing voltages. It will be understood that the angle of rotation (17) for both phasing circuits is arbitrarily chosen for purposes of illustrationand that in practice values widely different therefrom may be used by altering the constants of the phasing circuits 11 and 14.

The operation has so far been described upon the assumption that the polyphase voltage of the network 1 is balanced. Actually there may be an unbalance factor of a few percent in this voltage. The effect of a small degree of unbalance in the voltage of the network 1 is to slightly change the magnitude and phase position of the potential pole flux p (Fig. 2) as compared with the c-p'hase network voltage EC. This is equivalent to a slight rotation of the zero torque curves T11 and T14 and is of negligible importance in the operation of the protector.

The operation of the apparatus shown in Fig. 1 in response to incorrect feeder voltages may be set forth as follows: It is assumed that the network 1 is energized by balanced three-phase voltage of normal value, the circuit breaker 4 is open and the relay 5 is in the tripping position.

The incorrect feeder voltages which may be encountered in practice arise from the interchange of feeder cables in repairing feeder faults. As there are three feeder delta voltages, incorrect feeder voltages may be established by interchanging the A and B, B and C or A and C phase voltages and by rotating all three voltages 120 clockwise or 240 clockwise.

Referring to Fig. 3, the star voltages of the network 1 are denoted by the reference characters E1111, E1111 and Eon as in Fig. 2. In Fig. 3 however, the network star voltages are rotated for ccnvenience to the position in which the b-phase vector E1111 co-incides with the abscissa axis. The zero torque curves for the phasing circuits 11 and 14 are shown at T11 and T14 respectively, as in Fig. 2.

The triangle of delta voltages of the feeder corresponding to correct feeder voltages for the system of star voltages E1111, E1111 and E011 of Fig. 3 is shown in Fig. 4, in which the feeder delta voltages are denoted by the reference characters Es, EB and Ec.

If the feeder voltages EA and EB are interchanged, the delta voltages of the feeder 2 form the triangle shown in Fig. 5. The system of star voltages appearing at the secondary terminals of the transformer bank 3 in response to the in correct feeder voltages of Fig. 5 are shown at Ea, Eb and E0 in Fig. 3. It will be apparent from inspection of Fig. 3, that the voltage vector Eb does not intersect the curve T14 and the vector Es does not intersect the curve T11. ing circuits 11 and 14 accordingly produce strong tripping torques which maintain the relay 5 in open position.

If the feeder voltages EB and EC are interchanged, the resulting feeder delta voltages are I: as shown in Fig. 6. The corresponding relationship of star voltages is shown in Fig. '7. It will be seen that the vector E1, intersects the curve T14 and extends a short distance into the corresponding closing torque zone. intersect the curve T11 however, but terminates at a position to produce a strong tripping torque. The aggregate torque produced by the phasing Both phas-- The vector EC does not direction and the relay 5 remains open.

Figs. 8 and 9 show the voltage relationships for interchanged feeder voltages EA and E0, It will be apparent from Fig. 9 that the tripping torque producedby the phasing circuit 14 predominates over the closing torque produced by the phasing circuit 11, and the relay 5 remains open.

Figs. 10 and 11 show the voltage relationships when the feeder delta voltages are rotated 120 in the clockwise direction. Both phasing circuits 11 and 14 produce substantially maximum tripping torques, and the relay 5 is held open.

Figs. 12 and 13 show the voltage relationships when the feeder delta voltages are rotated 240 in the clockwise direction. In this case both phasing circuits 11 and l tproduce moderate tripping torques, and the relay 5 is held open. 7

Itwill be apparent from the above that the relay 5 can effect the closure of the circuit breaker 4 only when the network 1 is de-ene'rgized or the polyphase voltage of the feeder 2 is of correct phase sequence as compared to the polyphase voltage of the network 1.

Fig. 14 shows a modified phasing circuit which may be connected across the a-phase main contact members of the circuit breaker 4 as a substitute for the phasing circuit 14 of Fig. 1. In the Fig. 14 m'dification, a reactor 18 of high reactance as compared to the impedance of the phasing circuit 11 is included in the phasing circuit 19. The impedance of the phasing circuit 19 is preferably several times the impedance of the phasing circuit 11 and the phase angle of the circuit 19 preferably approaches 90. With the latter arrangement, the torque produced by the phasing circuit 11 predominates during normal conditions and the closing operation is controlled principally by the feeder and network c-voltages. The phasing circuit 19. operates to produce a tripping torque suificient to maintain the relay 5 open, in the event that the feeder a and b voltages or the feeder a and c voltages are reversed. Otherwise the operation of the Fig. 14 modification is the same as that described in connection with Fig. 1.

Fig. 15 shows a modification of the phasing circuit 11 of Fig. 1, in which an adjustable phasing resistor 20 is substituted for the phasing 1amp13 of Fig. '1, The operation of the apparatus shown in Fig. 15 will be obvious from that described above.

I do not intend that the present invention shall be restricted to the specific structural details, arrangement of parts or circuit connections herein set forth, as various modifications thereof may be effected without departing from the-spirit and scope of my invention. I desire, thereore, that only such limitations shall be imposed as are indicated in the appended claims.

I claim as my invention:

1. In an automatic protector for controlling the connection of a pair of polyphase alternatingcurrent circuits, a circuit breaker, means including a single-element relay for controlling said circuit breaker, said relay having a potential winding and a pair of windings in cooperative relationship with said potential winding, energizing means for said relay for effecting a closing operation of said circuit breaker when the polyphase voltages of said circuits are of the same phasesequence and a predetermined voltage relationship exists between said circuits and for preventing closure of said circuit breaker when the polyphase voltages of said circuits are of different phase sequence, said energizing means including phasing circuits for independently energizing said pair of windings in accordance with phasing voltages of different phase position derived from said circuits. 2. In an automatic protector for controlling the connection of a pair of polyphase alternatingcurrent circuits, a circuit breaker, means including a single-element relay for controlling said circuit breaker, said relay having a potential winding and a pair of windings in cooperative relationship with said potential winding,energizing means for said relay for effecting a closing operation of said circuit breaker when the polyphase voltages of said circuits are of the same phase sequence and a predetermined voltage relationship exists between said circuits and for preventing closure of said circuit breaker when the voltage of said polyphase circuits are of different phase-sequence, said energizing means including phasing circuits for independently energizing said pair of windings in accordance with phasing voltages of different phase position derived from said polyphase circuits and phase-sequence means for energizing said potential winding in accordance with a positive symmetrical component of the polyphase voltage of one of said polyphase circuits.

3. In an automatic protector for controlling the said relay are dependent upon a plurality of phase voltages of said circuits.

4. In an automatic protector for controlling the connection of a polyphase feeder circuit and a polyphase network circuit,- a circuit breaker, means including a single-element relay for controlling said circuit breaker; said relay having a winding and a plurality of phasing in cooperative relationship with said winding, means for energizing said winding in accordance with a positive potential windings potential potential symmetrical component of the polyphase voltage of said network circuit and means for energizing said phasing windings including a plurality of phasing circuits independently energized in accordance with voltages derived from a plurality of phases of said feeder circuit and said network circuit whereby the phasing characteristics of said relay are dependent upon a plurality of phase voltages of said feeder circuit and said network circuit.

5. In an automatic protector for controlling the connection of a three-phase feeder circuit and a three-phase network circuit, a circuit breaker, means including a single-element induction disc relay for controlling said circuit breaker, said relay having a potential winding and a pair of positionally displaced windings in cooperative relationship with said potential winding, means for energizing said potential winding, a first phasing circuit responsive to the difierence of voltage of a first phase of said feeder circuit and the cor j responding phase of said network circuit effective to produce a tripping torque in said relay if said first phase of voltage of said feeder circuit is interchanged with either of the remaining phases thereof, said first phasing circuit including one of said positionally-displaced windings, a second phasing circuit responsive to the difference of voltage of a second phase of said feeder circuit and the corresponding phase of said network circuit and effective to produce a tripping torque in said relay if said second phase of voltage of said feeder circuit is interchanged with either of the remaining phases thereof, said second phasing circuit including the remaining one of said positionally-displaced windings, whereby a tripping torque is produced in said relay in response to any incorrect phase relationship of the three-phase voltage of said feeder circuit as compared with the three-phase voltage of said network circuit.

6. In an automatic protector for controlling the connection of a three-phase feeder circuit and a three-phase network circuit, a circuit breaker, means including a single-element induction-disc relay for controlling said circuit breaker, said relay having a potential winding and a pair of positionally-displaced windings in cooperative relationship with said potential winding, means for energizing said potential winding, a comparatively low impedance phasing circuit responsive to the difference of voltage of a first phase of said feeder circuit and the corresponding phase of said network circuit for controlling the closing characteristic of said relay, said low impedance circuit including one of said positionally-displaced windings and being effective to produce a tripping torque in said relay if said first phase of the voltage of said feeder circuit is interchanged with either of the remaining phases thereof, a comparatively high impedance phasing circuit responsive to the difference of voltage of a second phase of the voltage of said feeder circuit and the corresponding phase of said network circuit, said high impedance circuit including the remaining one of said positionally-displaced windings and being effective to produce a tripping torque in said relay if said second phase of the voltage of said feeder circuit is interchanged with either of the remaining phases thereof, whereby a tripping torque is produced in said relay in response to any incorrect phase relationship of the threephase voltage of said feeder circuit as compared with the three-phase voltage of said network circuit.

MYRON A. BOS'I'WICK. 

